Quote:
Originally Posted by asphaltgambler
Also verify actual engine temp vs scan tool reading if you have a temp 'gun's to aim at the outlet of top radiator hose . Those are speed density systems ( no MAF ) so temp readings from coolant and inlet air with MAP needs to be right on money. If not typically the ECM firmware will 'fail' to slightly rich and you won't see it until the primary O2 sees it past the window.
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Thanks. Yes, it is speed/density EFI. No AMM present. IAT is plausible (5 deg higher than ambient) and coolant temp is on the money (90-100 deg C). Fuel pressure is not compensated for intake manifold pressure though. Compensation is done in ECU instead.
Fluctuating short term fuel trim is smoking gun that something is fishy with fuel pressure. I will try to find a nipple on fuel rail and measure pressure.